The present invention relates to a method of processing television pictures, in which the picture is divided into several parts and each picture part is examined in order to determine thereof--in the presence of a series of pictures succeeding each other in time--a movement vector.
It further relates to a device for processing pictures comprising a processor for determining--in the presence of a series of pictures succeeding each other in time--movement vectors associated with picture parts.
It finally relates to a television encoding system.
The present invention can be used in high-definition or ordinary television transmission/reception systems, in picture recording systems, for example those utilizing a laser readable disk, and in general in digital picture processing systems.
It is known from the conference entitled "Motion-compensated interpolation applied to HD-MAC pictures encoding and decoding" by F. Fonsalas and M. R. Haghiri, presented to the "Second International workshop on signal processing of HDTV", l'Aquila, Feb. 29-Mar. 3, 1988, to use such a method in a television transmission-reception system, in which complementary data of video data and especially movement vectors are transmitted by digital means designated as DATV (Digitally Assisted Television).
In the system proposed in that document, an encoding is utilized to reduce the sampling frequency with an associated flow rate of digital data reduced to the lowest possible value. For this purpose, the picture is divided into several parts, i.e. squares of 16.times.16 pixels, for each of which a mode of processing can be chosen among several modes, one of which utilizes movement vectors. For displaying the received pictures, the movement vectors are used to reconstruct an intermediate untransmitted picture between two transmitted pictures. In this case, the movement vectors have been determined at the encoding instant, that is to say that all the source pictures and especially those which will be suppressed by the encoding are still available, which permits of carrying out all the tests desirable for verifying the validity of the movement vectors, especially by comparing a picture reconstructed on the basis of the movement vectors with the corresponding source picture.
A particular problem arises when intermediate pictures should be formed at an instant at which the source picture by comparison is not available. This is the case, for example, when each time a supplementary picture should be introduced between two pictures for doubling the rate of display in order to diminish the flicker. When a picture has a periodical structure, for example, when it represents at least locally a raster or horizontal or vertical stripes, it is possible that several different vectors yield equivalent results for certain picture parts, that is to say that erroneous vectors can nevertheless yield correct results (no visible defects) for certain picture parts (this will be explained in detail hereinafter). However, if the chosen vector is erroneous for certain parts of the picture, while it is correct for other parts, there are visible defects at the transition between the parts which have a correct vector and those which have an erroneous vector.
It is known from the aforementioned document to use a cost function calculated over the 256 pixels of a picture part, which permits determining which is the most suitable among several movement vectors, but the estimation thus obtained does not permit eliminating the ambiguity when several movement vectors can be each used equally well for the same picture part, that is to say when several movement vectors exist, for which the aforementioned function of cost yields equivalent results. Such vectors will be designated as equivalent vectors.